Generally, various image-forming devices, such as copiers, fax machines, printers and the like are furnished with an amount of toner remaining detection system that senses the amount of toner remaining in a developer storage container, and when the amount of toner remaining falls below a preset reference value, indicates on an indicator part that the amount of toner remaining in the aforementioned developer storage container is too low.
Concerning such amount of toner remaining detection systems, those known in the past are such that an antenna is disposed in the developer storage container to sense the amount of toner remaining from the electrostatic capacitance of the remaining toner, for example in patent references Japanese Kokai Patent Application No. 2001-228697, Japanese Kokai Patent Application No. 2003-122107, and Japanese Kokai Patent Application No. 2004-086176. With those that use an antenna, as shown in FIG. 10 for example, a rod-shaped antenna (3) is disposed buried inside toner (Tn) to face developing sleeve (2b) inside toner storage container (2a) of developing unit (2) disposed close to image carrier (1), e.g., a photosensitive drum or the like. An electrostatic capacitance sensing circuit (3a) is connected to antenna (3), and an electrostatic capacitance sensing circuit (3c) is also connected to reference capacitor (3b) that is supplied with power from power source (2c) of aforementioned developing sleeve (2b). Then the electrostatic capacitance output from electrostatic capacitance sensing circuit (3c) on the capacitor (3b) side and the electrostatic capacitance output from electrostatic capacitance sensing circuit (3a) on the abovementioned antenna (3) side are compared by comparator (3d) and the amount of toner remaining in aforementioned toner storage container (2a) is sensed from the comparison result.
Detecting the electrostatic capacitance of the remaining toner with a sensing mechanism other than an antenna has also been proposed, as in Japanese Kokai Patent Application No. 2003-186296, for example, but in all cases, they are constituted so that the amount of toner remaining sensing signal obtained with any of these amount of toner remaining detection systems is received by a print control means (CPU) (4) on the printing and recording engine side, omitted from the figure, and approval/disapproval of the image-forming process is controlled by print control means (CPU) (4). That is, when it is judged that the amount of toner remaining sensed with the amount of toner remaining system described above has fallen below a preset reference value, the fact that the amount of toner remaining is too low is indicated on an operating and indication part, omitted from the figure.
However, in such a conventional amount of toner remaining detection system, two sensing signals, a sensing signal from antenna (3) and a sensing signal from power source (2c), are used as described above and the two sensing signals are compared. However, in the initial state of the two sensing signals, fluctuation is readily produced depending on the circuit board adjustment process during factory shipping and there is a risk of error in the sensing of the amount of toner remaining corresponding to the difference between the two sensing signals. For example, when the initial setting of the difference between the aforementioned two sensing signals is too large, images called white voids appear before indication that the amount of toner remaining is too low. And when the initial setting of the aforementioned two sensing signals is too small, indication that the amount of toner remaining is too low may occur even if a sufficient amount of toner remains.
For this reason, in the past, initial adjustment of the two sensing signals relating to the amount of toner remaining described above was strictly managed during factory shipping, but with such a strict adjustment process, there is a risk of reducing the overall device productivity.
The objective of the present invention is to provide an image-forming device that can basically eliminate the initial adjustment in the amount of toner remaining detection system.